DE60220083T2 - Cryptographic communication device - Google Patents

Description

Technical area

These The invention relates to a quantum cryptography communication device and a quantum cryptographic communication method which generates random number information while maintaining secrecy, share an eavesdropper based on the blur principle is detected in quantum mechanics.

State of the art

An overall configuration diagram in 5 illustrates conventional techniques, such as represented by the quantum cryptography first proposed by Gennett and Brassard in 1984 (Document 1: CH Gennett and G. Brassard, "Quantum Cryptography: Public Key Distribution and Coin Tossing" in Proc. IEEE International Conference on Computers , Systems and Signal Processing, Bangalo re, India, PP175-179, (1984), and Document 2: CH Gennett, F. Bessette, G. Brassard and L. Salvail "Experimental Quantum Cryptography", J. Cryptology, p. 3 to 28, (1992).

In 5 is a quantum-end device 100 a device which transmits a ciphertext by using the quantum cryptography, and a quantum receiving device 200 is a device that receives the ciphertext using quantum cryptography. A quantum cryptography communication channel 1 is a communication channel for transmitting a qubit from the quantum sending device 100 to the quantum receiving device 200 ,

Here the qubit contains arbitrary two-level states:
| 0>, 1>.

The qubit is a quantum state in which a uniform, linear superposition of the states
α | 0> + β1>
allowed is. In particular, in the field of quantum cryptography communication, a polarization state, a phase state, etc. of a photon is often used to represent a state of the qubit.

A classic communication network 2 connects the quantum sending device 100 and the quantum receiving device 200 , The classic communication network 2 is a network to perform communication between the two devices by a conventional communication method.

The secret shared information 3 and the secret information 21 are information which is secret between the quantum sending device 100 and the quantum receiving device 200 were shared in advance. It is an object of quantum cryptography, random information, which is much larger than the above-mentioned secretly shared information, between the quantum sending device 100 and the quantum receiving device 200 while maintaining secrecy.

A qubit generating agent 4 gives a predefined qubit
| 0>
periodically off.

One Random number generating means 5 outputs a first random number bit out.

One Random number generating means 6 outputs a second random number bit out.

One Quantum encoder X7 leads quantum coding of the qubit produced by the qubititer agent 4 has been generated in accordance with the first random number bit generated by the random number generation means 5 has been issued by. The quantum coding rule will be described below described.

If the first random number bit is 0, an identity transformation: | 0> <0 | + | 1> <1 |.

If the first random number bit is 1, an X transformation: | 0> <1 | + | 1> <0 |.

The X-transformation in the above rule is a bit-flip transformation and an x-element in the Pauli matrix corresponds to the X-transformation.

One Quantum modulation means H8 leads a quantum modulation of the qubit, with which with the quantum encoding means X7 a quantum coding has been performed, in accordance with the second random number bit generated by the random number generation means 6 has been issued by. The modulation rule will be below described.

If the random number bit is 0, an identity transformation: | 0> <0 | + | 1> <1 |.

If the random number bit is 1, an H transformation: (| 0><0 | + | 1><1 | - | 1><1 |) / √ 2 ,

The H transformation in the above rule is a Hadamard transformation and the H transformation corresponds to a base transformation.

As shown above, is a protocol for transmitting the qubit, which Two conjugate bases of the + base and the × base are used, referred to as the BB84 protocol. The two conjugate bases of + base and × base will be described later.

Moreover, compared to the BB84 protocol above, where the qubit has been transmitted using two modulation rules from the identity transformation and the H transformation, in the six-state quantum cryptography (Document 3: D. Bruss. Optimal Eavesdropping in Quantum Cryptography with Six States ", Phys. Rev. 81, pp. 3018-3021, (1998)), the modulation is performed using three bases (modulation rules) in which a phase · Hadamard transform, SH: (| 0><0 | + | 0><1 | + i | 1><0 | - i | 1><1 |) / √ 2 is added to the transformations used for quantum modulation. In this case, the three base transforms mentioned above are chosen for the second random number, which assumes three values of 0, 1 and 2.

A basic replacement 9 performs a classic communication with the quantum receiving device 200 for the first random number generated by the random number generation means 5 has been issued, and extracts random division information.

An error correction tool 10 performs the classical communication with the quantum receiving device 200 through the classic communication network 2 for the randomization information generated by the basic exchange means 9 has been issued by, and performs an error correction.

A classic means of communication with authentication 11 will be provided, so that the basic exchange means 9 and the error correction means 10 the classical communication with the quantum receiving device 200 carry out. As will be described explicitly in Document 1 and Document 2, the information shared in secret becomes 3 for authentication by the classical means of communication with authentication 11 used.

A confidentiality reinforcing agent 12 amplifies the secrecy of the error corrected random division information obtained from the error correction means 10 has been issued.

An eavesdropping detection unit 13 judges whether there has been a eavesdropping attack based on additional information provided by the error correction means 10 has been issued.

A secret key 14 is a key used by the privacy-enhancing agent 12 is output and with the quantum receiving device 200 while maintaining secrecy with the quantum receiving device 200 is shared.

A random number generator 22 outputs a third random number bit.

A quantum demodulation means H23 performs quantum demodulation for the quantum cryptography communication channel 1 transmitted qubit in accordance with the third random number bit, which of the random number generation means 22 has been issued by. A demodulation rule will be described below.

If the random number bit is 0, an identity transformation: | 0> <0 | + | 1> <1 |.

If the random number bit is 1, an H transformation: (| 0><0 | + | 0><1 | + | 1><0 | - | 1><1 |) / √ 2 ,

Moreover, in six-state quantum cryptography, demodulation is performed by using three bases by performing a Hadamard · antiphase transformation, HS ^-1 : (| 0><0 | + i | 0><1 | + | 1><0 | - i | 1><1 |) / √ 2 to the transformations used for the quantum demodulation. In this case, the above three base transforms are selected for the random numbers having three values of 0, 1, and 2.

A quantum measuring device 24 performs a quantum measurement for the qubit with which the quantum demodulation has been performed. As a result of measurement becomes
for Qubit | 0>"0" output and
for qubit | 1>"1" output.

Especially in a case where a polarization state of a photon as For example, the qubit can be easily used by it a polarization beam splitter and two photon detectors will be realized.

A base substitute 25 performs the classic communication with the quantum-end device 100 and extracts the random division information with reference to the measurement result obtained from the quantum measuring means 24 and the third random number generated by the random number generating means 22 has been issued.

An error correction tool 26 performs the classic communication with the quantum-end device 100 and performs an error correction with reference to the random division information obtained from the base exchange means 25 has been issued by.

A classic means of communication with authentication 27 is provided to the classical communication with the quantum transmission device 100 at a time of use of the base replacement agent 25 and the error correction means 26 perform. The secret shared information 21 is used for authentication with the quantum sending device 100 used.

A confidentiality reinforcing agent 28 enhances the secrecy of the random division information to which error correction has been applied.

An eavesdropping detection unit 29 judges whether a eavesdropping attack has been performed based on additional information provided by the error correcting means 26 has been issued.

A secret key 30 is a key used by the privacy-enhancing agent 28 is output and with the quantum sending device 100 shared, with the secrecy with the quantum sending device 100 is maintained.

below the functionality is explained.

An overall diagram of the process in 6 shows the conventional technique of the quantum cryptography communication method, which is described in document 1 and document 2 is pictured.

The whole process can be divided into two big steps, ie a big step of quantum cryptography communication (S100) and a big step of classical data processing (S200). The processing on a left side is by the quantum sending device 100 performed and the processing on a right side is by the quantum receiving device 200 carried out.

The big step of quantum cryptography communication (S100) is a step of transmitting a qubit string from the quantum sending device 100 to the quantum receiving device 200 represents.

For each Qubit, the following six steps (S11-S16) are repeated.

First, in a qubit generating step (S11), the qubit generating means is generated 4 periodically a predefined qubit
| 0>.

Thereafter, in a quantum encoding step (S12), the quantum encoding means X7 encodes the generated qubit based on the first random number bit generated by the random number generating means 5 has been issued.

In a quantum modulation step (S13), the quantum modulation means H8 modulates the coded qubit based on the second random number bit generated by the random number generation means 6 has been issued.

By this modulation, the qubit becomes a modulation bit having four states first random number 0 1 + Base | 0> | 1> × base (| 0> + | 1> / √ 2 (| 0> - | 1> / √ 2 which represent 0 and 1 by means of two pairs of shared conjugate bases (+ base and × base).

In a quantum transfer step (S14), the above modulation bit becomes the quantum sending device 100 to the quantum receiving device 200 through the quantum cryptography communication channel 1 Posted.

In a quantum demodulation step (S15), the quantum demodulation means H23 demodulates the transmitted Qubit (modulation bit) based on the third random number bit generated by the random number generation means 22 has been issued.

Here can be known by using a characteristic that when the identity transformation and the Hadamard transform, which in quantum modulation and the quantum demodulation have been used twice the transformation to identity transformation becomes that only if the second random number and the third random number are identical are and the same transformation for quantum modulation and the quantum coding is used, the quantum coding is performed, and the quantum modulation of the qubit, with which a quantum modulation carried out is done correctly.

In a quantum measuring step (S16), the quantum measuring means passes 24 a quantum measurement of the qubit with which quantum demodulation has been performed. In the quantum measurement, if the qubit is | 0>, bit "0" is output, and if the qubit is | 1>, bit "1" is output.

Accordingly, become only when the quantum demodulation in the quantum demodulation step (S15) done correctly a measurement bit and the first random number bit have been identical. When the quantum demodulation has been erroneously performed, the measurement bit becomes with the first random number bit with only one probability identical by 1/2.

As described above ends the big step of quantum cryptography communication (S100) after repeating the six steps from the qubit generation step (S11) until the quantum measuring step (S16) for all qubits.

In the big one Step of classical data processing (S200) become the following four steps performed.

First, in a basic exchange processing step 21 Basic information, second random number bit information, and third random number bit information used for the quantum modulation and the quantum demodulation in transmitting the qubit, which has been performed in the large step of quantum cryptographic communication (S100), between the quantum sending device and the quantum receiving device through the classic communication network 2 replaced. At this time, if the exchanged basic information is identical, it is known that the correct quantum mo dulation and the correct quantum demodulation have been performed. Accordingly, only the first random number bit and the quantum measuring bit in the transmission of a qubit in which the basic information is identical and a correct quantum modulation and a correct quantum demodulation have been performed are extracted and output as random dividing information. Since one-half of the basic information is not identical, approximately one-half of the qubits that arrive at the quantum-end device become 100 to the quantum receiving device 200 have been transferred, invalid. In the six-state quantum cryptography of document 3, about 2/3 of the transmitted qubits become invalid.

In classical communication, which is used in this step, an eavesdropping action can be bypassed. However, interference by a third party must be prevented. If hitting is allowed, an eavesdropped device will function in each of the quantum cryptography communication channels 1 and the classic communication network 2 containing the quantum-end device 100 and the quantum receiving device 200 connect, as a relay. The device owned by the eavesdropper may be considered a false quantum receiving device 200 for the quantum transmission device 100 act and as a wrong quantum sending device 100 for the quantum receiving device 200 act. Accordingly, an attack becomes possible in which a secret key is respectively interposed between the quantum sending device 100 and the device of the eavesdropper and between the device of the eavesdropper and the quantum receiving device 200 is shared, the quantum transmission device 100 sends a ciphertext by using the key shared in quantum cryptographic communication by using the device of the eavesdropper as the corresponding quantum receiving device 200 and the device of the eavesdropper deciphers the cipher text by holding the key, which with the quantum sending device 100 has been used, re-encrypted, by using the secret key, which with the quantum receiving device 200 has been shared, and sends the ciphertext to the quantum receiving device 200 , Accordingly, in order to prevent the interference by the third party, authentication must be performed using the secret shared information which has been secretly shared in advance between the quantum sending device and the quantum receiving device.

in the Generally, in the quantum transfer step (S14), even if the device of the eavesdropper transmitted Qubit does not always listen, the device of the eavesdropper perform correct quantum demodulation as the device of the Lauschers the basic information, which is used for the quantum modulation has not known. If the quantum demodulation is performed incorrectly, the transmitted one changes Qubit into a qubit in a completely different state according to the blur principle in of quantum mechanics. Accordingly, remains a trace of the eavesdropping.

In an error correction step (S22), the error is corrected based on the random division information output in the base exchange processing step (S21), while the classical communication allowing the eavesdropping but not allowing the intermingling and the asserting of the classic communication network 2 between the quantum-emitting device and the quantum-receiving device. Accordingly, the authentication must be performed by using the secret shared information which has been secretly shared between the quantum sending device and the quantum receiving device in advance. Moreover, data processing is performed in which the error correction is performed, but the amount of information leaked to the third party is low and secrecy is maintained. At this time, a bit rate and a bit error rate are output as additional information. Based on a size, change, etc., from this value, it is judged whether there has been a eavesdropping attack.

In a privacy enhancement processing step (S23) becomes the secrecy of the information regarding the scope of information strengthened by hashing the error-corrected random-division information is applied.

In an updating step for secret information (S24) becomes the secret shared information for one next Quantum cryptography communication is updated by adding part of the Random division information whose secrecy has been strengthened is, is used, and remaining random division information is considered a secret key output.

Furthermore becomes a procedure of outputting the random division information from the above secret shared information in the conventional one Cryptography that does not conform to quantum cryptography, briefly explained.

In In this case, secretly shared information which is secret in advance shared between a transmitting device and a receiving device has been used as an encryption key and a decryption key, an enciphering communication of random information, which is larger as the above secret information is performed by Common key block cryptography, data stream cryptography etc. is used and the random information is shared while the Secrecy is maintained.

however There is no eavesdropping detection function in conventional cryptography. Accordingly, the Listener cryptographically the random information that encodes has been analyze, if the eavesdropper has a processing in a sufficiently large one computer-aided Scope can perform. In particular, in conventional cryptography secrecy the random division information which has been transmitted, only secured based on the security of the computerized scope. Meanwhile is used in quantum cryptography when the eavesdropping attack is based detected on the eavesdropping detection function according to quantum mechanics is discarded, the communication and a processing like that Repeating the communication is performed until it is confirmed that there is no eavesdropping, accordingly the secrecy is based secured on the security of the information volume of the transmitted qubit, for the It is guaranteed that there was no eavesdropping.

In the conventional quantum cryptography communication device and in the conventional quantum cryptography method Problem is that the authentication is done in classic communication must, by the secretly shared information, which prepares in advance has been used. Furthermore There is a problem in that the basic exchange, in which Information about the Quantum modulation and quantum demodulation between the transmitting device and the receiving device via the classic communication network is exchanged must be a valid one Bits from the measurement bit which are obtained in the quantum communication is about to extract, and consequently goes about one half (approximately 2/3 in a case of six-state quantum cryptography) of the qubit strings, with which quantum transfer carried out has been lost.

Furthermore there is a problem that secrecy is threatened in dependence from the processing capacity of the eavesdropper in terms of computerized scope, since there is no Eavesdropping detection function in conventional cryptography gives.

Barbosa et al reveal in "Secure communication using coherent states ", Proceedings of the Sixth International Conference on Quantum Communication, Measurement and Computing, QCMC-02, [Online] July 2002 [2002-07], pp. 1-3, XP002307214 from the Internet: URL: http://citebase.eprints.org/cgi-bin/citations?id=oai:arXiv.org:quant-ph/0210089> [retrieved 2004-11-23] a secure communication system using coherent states using a shared secret key for key extension. This becomes a secret key used to set the parameters of a multimodal coherent state to modulate, and the current key is used to the Polarization basis from the given set of two-mode bases specify.

Nishioka et al reveal in "Circular Type Quantum Key Distribution "IEEE Photonics Technology Letters, IEEE Inc. New York, US, Vol. 14, No. 4, April 2002 (2002-04), pp. 576-578, XP001122905 ISSN: 1041-1135 a Quantum key distribution of the circular type, which is based on an interferometric system used on two Mach-Zehnder interferometers.

Yamamura et al also reveal in "Error detection and authentication in quantum key distribution ", Information Security and Privacy, Australasian Conference, ACISP, XX, XX, No. 2119, 6. August 2001 (2001-08-06), pp 260-273, XP002957601 an error detection and in a raw key an authentication of a secret key in the quantum key distribution based on collision-free neighborhood functions and error correction codes, like Reed-Solomon codes.

It is an object of this invention, a quantum cryptography communication device and a quantum cryptography communication method which does not require authentication in the classical Communication, still need the base exchange and which, moreover, all the transmitted Qubits for signal transmission to be able to use, while the secrecy of the transmitted Qubits related to the amount of information by the eavesdropping detection function is maintained.

Disclosure of the invention

The The object described above is achieved by a quantum-emitting device according to claim 1, a quantum receiving device according to claim 2, a quantum cryptography communication system according to claim 3, a quantum cryptographic communication method according to claim 6 and also solved by their respective dependent claims.

Brief description of the drawings

1 shows an overall diagram of the configuration of the first embodiment.

2 shows a quantum cryptographic communication method of the first embodiment.

3 shows an overall diagram of the configuration of the second embodiment.

4 shows an overall diagram of the configuration of a third embodiment.

5 shows an overall diagram of the configuration of the quantum cryptography according to the prior art.

6 FIG. 12 is a diagram illustrating a prior art quantum cryptographic communication method. FIG.

Best embodiment for the present invention

First embodiment.

1 shows an overall diagram of the configuration of the first embodiment.

In 1 are the quantum-end device 100 and the quantum receiving device 200 via the quantum cryptography communication channel 1 for transmitting a qubit from the quantum well device 100 to the quantum receiving device 200 connected.

The classic communication network 2 is a communication network connecting the quantum sending device and the quantum receiving device.

The secret shared information 3 and the secret information 21 are secret information which has been previously shared between the quantum sending device and the quantum receiving device.

An internal configuration of the quantum sending device 100 will now be explained.

A qubit generation unit 40 outputs a predefined qubit | 0> periodically. Here, as the qubit, a polarization state of a photon which is a horizontal polarization state | H> for Qubit | 0> and which is a vertical polarization state | V> for qubit | 1> can be selected. As the qubit, a phase state may also be selected in a case where an interference system has been constructed. In addition to the photon, it is also possible to select any two-level states, such as an electron.

In a case where the polarization state of the photon has been selected, the illustrated qubititer formation unit 40 can be easily realized by placing a polarizer at the output of a light source.

A random number generation unit 50 represents a unit that outputs a first random number bit.

A first pseudorandom number generation unit 60 represents a unit that outputs a first pseudorandom number bit by the secret shared information 3 used as a seed.

A quantum coding unit 70 represents a unit which quantizes the qubit with the qubit, which by the qubit production unit 40 has been generated based on the first random number bit generated by the random number generation unit 50 has been issued. The coding rule is as follows:
if the random number bit is 0,
an identity transformation: | 0><0 | + | 1><1 |, and
if the random number bit is 1,
an X-transformation: | 0><1 | + | 1><0 |.

For example can it in a case where the polarization state of the photon selected as the qubit is simply realized by a polarization modulator or a phase modulator is installed, leaving a 45 degree polarization state in the TE mode (transverse electric polarization wave of engl. transverse electric polarization wave) is transmitted and in the on / off based on the first random number bit.

A quantum modulator 80 represents a unit which a quantum modulation for the qubit, with the quantum coding by means of the quantum coding unit 70 has been performed based on the first pseudo-random number bit generated by the first pseudo-random number generation unit 60 has been issued. The modulation rule is as follows
if a pseudorandom number bit is 0, an identity transformation: | 0><0 | + | 1><1 | and,
if a pseudorandom number bit is 1, an H transformation: (| 0><0 | + | 0><1 | + | 1><0 | - | 1><1 |) / √ 2 ,

The H transformation is a Hadamard transformation and the H transformation corresponds to the base transformation.

Moreover, in the six-state quantum cryptography, in comparison with the above BB84 protocol in which transmission of the qubit has been performed using two conjugate bases, the modulation is performed by using three bases by performing one phase. Hadamard transform,
SH: (| 0><0 | + | 0><1 | + i | 1><0 | - i | 1><1 |) / √ 2 is added to the transformations used for quantum modulation. In this case, the above three base transforms are selected for the first random numbers having three values of 0, 1 and 2. In particular, the above transformation of the polarization state of the photon can be easily obtained by using the phase modulator by adjusting the phase modulator such that a TE mode level of the phase modulator and a horizontal plane of polarization in the polarization state make an appropriate angle and by proper phase modulation only for TE mode.

A first error correction unit 90 represents a unit which is a classical communication with the quantum receiving device 200 and which error correction with respect to the first random number generated by the random number generation unit 50 has been issued. This output becomes the error-corrected random division information.

A first classic communication unit 130 is a unit which is provided so that the first error correcting unit 90 the classical communication with the quantum receiving device 200 can perform. In this embodiment, the pseudorandom number which of the secret shared information 3 and secretly shared information 21 was generated by the quantum transmission device 100 and the quantum receiving device 200 divided. Accordingly, an authentication function is not necessarily needed.

A first secrecy reinforcement unit 110 represents a unit that enhances the secrecy of the error-corrected random division information.

A first eavesdropping detection unit 120 is an eavesdropping detection unit based on the additional information provided by the first error correction unit 90 is issued, judges whether there has been a eavesdropping attack.

The secret key 14 is a key used by the first privacy-enhancing unit 110 is issued and shared while maintaining secrecy with the quantum receiving device 200 is maintained.

Below will be an internal configuration of the quantum receiving device 200 explained.

A second pseudorandom number generation unit 220 is a unit which has a second pseudo-random number in synchronism with the first pseudo-random number generation unit 60 issues by the secret shared information 21 is used as a seed.

A quantum demodulator 230 is a unit which provides a quantum demodulation for the qubit transmitted through the quantum cryptography communication channel 1 has been transmitted based on the second pseudo-random number bit generated by the second pseudo-random number generation unit 220 has been issued. The demodulation rule is as follows
if the pseudorandom number bit is 0, an identity transformation: | 0><0 | + | 1><1 | and
if the pseudorandom number bit is 1, an H transformation: (| 0><0 | + | 0><1 | + | 1><0 | - | 1><1 |) / √ 2 ,

Moreover, in six-state quantum cryptography, demodulation is performed by using three bases by performing a Hadamar · antiphase transformation, HS ^-1 : (| 0><0 | + i | 0><1 | + | 1><0 | + i | 1><1 |) / √ 2 is added to the transformations used for the quantum demodulation. In this case, the three basic transforms above are selected for the second pseudo-random numbers having three values of 0, 1 and 2.

A quantum measuring unit 240 is a unit which performs a quantum measurement for the qubit with which quantum demodulation has been performed. As the measurement becomes
for Qubit | 0>"0" output, and
for Qubit | 1>"1" is output.

A second error correction unit 250 is a mechanism which is the classical communication with the quantum transmission device 100 performs and which an error correction with respect to the measurement result, which of the quantum measuring unit 240 has been issued. This output becomes the error corrected random division information.

A second classic communication unit 260 represents a unit which is provided so that the second error correcting unit 250 the classic communication with the quantum-end device 100 can perform. The authentication function is not necessarily needed like the first classical communication unit 130 ,

A second secrecy enhancement unit 270 is a unit which enhances the secrecy of the error-corrected random division information.

A second eavesdropping detection unit 280 represents a unit based on the additional information provided by the second error correction unit 250 is issued, judges whether there has been a eavesdropping attack.

The secret key 30 is a key used by the second secrecy enhancement unit 270 and which is shared while maintaining secrecy with the quantum broadcasting device 100 is maintained.

following the way of working is explained.

2 is a diagram of the overall process.

Of the entire process can be in two big Steps are divided, i. a big step in quantum cryptography communication (S300) and a big one Step of classical data processing (S400).

Of the size Step of Quantum Cryptography Communication (S300) is a step of transferring a qubit string from the quantum send device to the Quantum receiving device. For each qubit will be repeated the following six steps.

In a quenching generating step (S31), the qubit production unit generates 40 a predefined qubit
| 0>
periodically.

In a quantum coding step (S32), the quantum coding unit codes 70 the produced qubit ba based on the random number bit generated by the random number generation unit 50 has been issued.

In a quantum modulation step (S33), the quantum modulator modulates 80 the coded qubit based on the first pseudo-random number bit, which is from the first pseudo-random number generation unit 60 has been issued. By this modulation, the qubit takes on four states representing 0 and 1 over two pairs of shared conjugate bases. pseudo-random number 0 1 + Base | 0> | 1> × base (| 0> + | 1>) / √ 2 (| 0> - | 1>) / √ 2

In a quantum transfer step (S34), the above modulation bit becomes the quantum sending device 100 to the quantum receiving device 200 through the quantum cryptography communication channel 1 transfer.

In a quantum demodulation step (S35), the quantum demodulator demodulates 230 the transmitted qubit based on the second pseudo-random number bit generated by the second pseudo-random number generation unit 220 has been issued.

In In this embodiment, the first pseudo-random number bit, which has been generated in the quantum modulation step (S33), and the second pseudorandom number bit which is in the quantum demodulation step (S35) has been generated, synchronized. Accordingly, in contrast to conventional art in which about 1/2 (2/3 in six-state quantum cryptography) the transmitted Qubit strings invalid in the quantum cryptography communication method according to this Embodiment, the correct quantum demodulation performed constant.

In a quantum measuring step (S36), a quantum measurement of the qubit with which a quantum demodulation has been performed is performed. In quantum measurement,
if the qubit is | 0>, bit "0" is output, and
if the qubit is | 1>, bit "1" is output.

Accordingly, in the quantum demodulation step (S35), the quantum demodulation always done correctly. Accordingly, as long as the qubit, which transmit no turbulence due to noise and no eavesdropping action happens, the measurement bit always identical to the random number bit, which has been generated in the quantum coding step (S32).

To repeating the above six steps from S11 to S16 for all of Qubits ends the big step quantum cryptography communication (S300).

following be in the big one Step of the classical data processing (S400) the following three Steps performed.

In an error correction processing step (S41), the error is corrected based on the random number bit generated in the quantum encoding step (S32) and the measurement bit measured in the quantum measurement step (S36), while the classical communication allowing a eavesdropping attack is corrected via the classic communication network 2 the quantum-emitting device and the quantum-receiving device is performed. Although the error correction is performed, data processing is performed so that the amount of information leaked to the third party is small and secrecy is maintained. At this time, as the additional information, a bit rate and a bit error rate are output. Based on a size, change, etc., from this value, it is judged whether a eavesdropping attack has occurred. In a case of this invention, the quantum modulation and the quantum demodulation are based on the secret shared information 3 and secretly shared information 21 in the large step of quantum cryptography communication (S300).

Accordingly, in classical communication a consistent error correction processing impossible, even if meddling and putting are allowed, and the eavesdropper can be detected without error.

Accordingly, since the compound attack which is conventional in the prior art is not possible, the authentication function in the classical communication is not necessarily needed.

Furthermore can in a case where the eavesdropper the qubit, which in the Quantum transfer step (S34) will, catch, the eavesdropper the quantum modulation information due to the pseudo-random characteristic not predict. Furthermore It is due to the random characteristic of the quantum coding information completely impossible, meaningful information of a qubit, of which the characteristic, that the qubit can not be copied by quantum mechanics has been proven to extract. In addition, the eavesdropping act from the turbulence, which is unavoidable by the eavesdropping act caused to be detected.

In the privacy enhancement processing step (S42) is the secrecy in a way of information strengthened by the hash function on the error-corrected random division information, which of the error correction processing step (S41) has been issued.

in the Update step for secretly shared information (S43) becomes the secretly shared information updated by adding a part of the random division information, from which reinforces the secrecy has been, for a next one Quantum cryptography communication is used and left over Random division information is output as a secret key.

As shown, a quantum cryptographic communication apparatus according to this embodiment, in which detection of eavesdropping based on quantum mechanics is performed by using the quantum communication channel 1 for performing first signal transmission, includes quantum states which can not be concurrently observed simultaneously, and the classic communication network 2 for performing a second classical information data communication in which the quantum sending device 100 and the quantum receiving device 200 can prevent the interference and the insertion in the classical communication by the secretly shared information 3 and the secret information 21 , which have been securely maintained in advance, are used, and in which the quantum-end device 100 and the quantum receiving device 200 can safely and secretly share the random data, the quantum sending device 100 and the quantum receiving device 200 , The quantum-end device 100 includes the qubititer unit 4 which can constantly generate a qubit in an identical quantum state, the random number generation unit 50 which is a signal source for quantum coding applied to the qubit, is the first pseudorandom number generation unit 60 which the secret shared information 3 treated as a seed and generates the pseudorandom number from that seed, the quantum coding unit 70 , which with the qubit is a quantum coding based on the random number generated by the random number generation unit 50 has been issued, performs a quantum modulator 80 which is associated with the qubit based on the pseudo-random number generated by the first pseudo-random number generation unit 60 has been output, performs quantum modulation, the first error correcting unit 90 which performs error correction while the classical communication with the quantum receiving device 200 while maintaining secrecy, a first classical communication unit 130 , which performs the classical communication, the error correction processing with the quantum reception device 200 perform the first privacy-enhancing unit 110 which amplifies the secrecy of the secret information whose error has been corrected, and the first eavesdropping detection unit 120 which performs the listening based on the additional information output in the error correction processing.

Moreover, the quantum receiving device includes 200 the second pseudorandom number generation unit 220 which the secret shared information 21 treated as a seed and generates a pseudorandom number from that seed, the quantum demodulator 230 which performs demodulation by performing quantum modulation of the received qubit based on the pseudo-random number generated by the second pseudo-random number generation unit 220 is performed, a quantum measuring unit which measures the demodulated qubit and outputs a classical bit, the second error correcting unit 250 which performs error correction after the quantum communication ends while the classical communication with the quantum sending device 100 while maintaining secrecy, the second classic communication unit 260 which performs classical communication to the error correction processing with the quantum sending device 100 a second privacy-enhancing unit which enhances the secrecy of the secret information from which the error is corrected, and the second eavesdropping recognition unit 280 which one Listening attack detected based on the additional information that is output in the error correction processing.

Moreover, the quantum cryptography communication method illustrated in this embodiment includes
a major step in quantum cryptography communication which, for each qubit, comprises a group of steps of a generating step for generating a qubit by the qubit generating unit 4 a quantum encoding step of performing quantum coding on the generated qubit based on the random number bit generated by the random number generation unit 50 a quantum modulating step is performed for performing quantum modulation of the qubit with which quantum coding is performed based on the pseudorandom number bit generated by the first pseudorandom number generation unit from the secretly shared information 3 is generated as a seed of a quantum transferring step for transferring the qubit, with which quantum modulation is performed, from the quantum sending device 100 to the quantum receiving device 200 via the quantum communication channel 1 a quantum demodulation step of performing quantum demodulation on the received qubit, and a quantum measuring step of performing quantum measurement on the qubit with which demodulation is performed;
and a major step in classical data processing, including a group of steps of an error correction processing step to perform error correction over the classical communications network 2 for the classical data obtained as a result of the communication of a qubit string, a secrecy enhancement processing step for performing the secrecy enhancement by the quantum sending device and the quantum receiving device respectively for the classical data with which the error correction is performed and an updating step for the secret information for updating a part of the classical data with which the secrecy enhancement is performed as the secret shared information.

In this embodiment will be quantum modulation and quantum demodulation based on the pseudo random number bit synchronously under Use of secret shared information as a seed between the Quantum and the quantum receiving device output is carried out. Accordingly, the Base exchange unit and the base replacement processing step, which exists in the conventional art, omitted become.

Accordingly, everyone can the qubits are used effectively instead of about 1/2 (2/3 in the six-state quantum cryptography) the transmitted Qubit strings invalid and a high-speed characteristic the bitrate twice (or three times) those of the conventional one State of the art, can realized who the.

Especially is in six-state quantum cryptography (12.7%), which is a higher allowed bit error rate to secure the security compared to the BB84 protocol (11%) (Document 4: H.-K. Lo, "Proof of unconditional security of six-state quantum key distribution scheme ", quant-ph / 0102138 LANL-preprint), the transmission efficiency according to the conventional The prior art as low as 1/3, whereas the transmission efficiency according to this Invention is three times higher, and the transmission efficiency, which not less than the BB84 protocol can be realized.

Furthermore It is because the quantum modulation and the quantum demodulation are performed by the secret shared information, which is in advance between the quantum sending device and the quantum receiving device is shared, is used equal to the authentication in the big step the quantum cryptography communication (S300) is performed, and it is not necessary the authentication communication Furthermore in the big one How to perform classical data processing (S400) step it is the case in the conventional art.

Furthermore it is through the eavesdropping detection function possible, to confirm, if there was a eavesdropping attack. Accordingly, the security of the transmitted Qubits be ensured without eavesdropping. in terms of the Amount of information. So it is possible to share the secrecy of very safe random information in comparison to conventional cryptography, which is based on the Safety with regard to of the calculation scope.

In This embodiment is quantum cryptography communication realized by a polarization state of any qubit as an actual one Example is applied.

however can the quantum cryptography communication be carried out by applying a phase state of any qubit.

Embodiment 2.

In This embodiment, an embodiment is described, in a phase state of a photon is applied as a qubit and in which the quantum cryptography communication is performed, by using a Mach-Zehnder inferferometer.

3 shows an overall configuration diagram of the second embodiment. A Mach-Zehnder interferometer 900 includes the qubititer unit 40 , a first phase modulator 81 , a quantum communication channel 101 , a quantum communication channel 102 , the quantum measuring unit 240 and a second phase modulator 231 , The configuration of the qubit generation unit, the quantum coding unit, the quantum modulator, the quantum communication channel, the quantum demodulator, and the quantum measurement unit is different from the configuration in Embodiment 1.

below become component parts, which differ from the design form 1, described.

The qubit production unit 40 includes a single photon source 700 , a beam splitter 350 and a mirror 400 ,

A photon coming from the single photon source 700 is output through the beam splitter 350 and the mirror 400 divided into two optical paths. A state in which the photon in the higher quantum communication channel 101 is, is called
| U>
defines and a state in which the photon in the deeper quantum communication channel 102 is, is called
| L>
defined, then a qubit to be generated can be described as
| 0> = (| u> + | l>) / √ 2 ,

The first phase modulator 81 corresponds to the quantum coding unit and the quantum modulator in the embodiment 1 , The first phase modulator 81 performs quantum coding and quantum modulation of the generated qubit based on the first random number bit generated by the random number generation unit 50 and the first pseudo-random number bit generated by the first pseudo-random number generation unit 60 by, so that when the random number bit is 0 and the pseudorandom number bit is 1, | 0> = (| u> + | l>) / √ 2 . if the random number bit 1 is and the pseudorandom number bit is 0, | 1> = (- | u> + | l>) / √ 2 . if the random number bit is 0 and the pseudorandom number bit is 1, | 0 > = (i | u> + | l>) / √ 2 , and if the random number bit is 1 and the pseudorandom number bit is 1, | 1 > = (-I | u> + | l>) / √ 2 ,

A quantum transfer of the qubit, with which quantum coding and quantum modulation have been performed, to the quantum receiving device 200 is through the quantum communication channel 101 carried out.

Quantum demodulation of the transmitted qubit is done by means of the second phase modulator 231 , which corresponds to the quantum demodulator in Embodiment 1, performed based on the second pseudo-random number bit which is generated by the second pseudo-random number generation unit 220 which is synchronized with the first pseudo-random number generation unit 60 in accordance with the following rule.

If the pseudorandom number bit is 0, identity transformation: | u> <u | + | l> <l |, and if the pseudorandom number bit is 1, phase transformation S: | u> <u | + i | l> <l |.

At this time, since the first pseudorandom number bit and the second pseudorandom number bit are identical as shown above, the above qubit with which a quantum demodulation has been performed is
| 0> = (| u> + | l>) / √ 2 if the random number bit is 0, and
| 1 > = (- | u> + | l>) / √ 2 if the random number bit is 1,
based on the first random number bit.

In the quantum measuring unit 240 which a mirror 241 , a beam splitter 242 , a first photon detector 243 and a second photon detector 244 has, detected,
if the qubit is | 0>, the first photon detector 243 the photon, and detected,
if the qubit is | 1>, the second photon detector 244 the photon.

The other configuration besides the above is completely the same as in the embodiment 1 ,

As stated above, even in a case where the phase state of the photon is applied as the qubit, and the quantum cryptography communication is performed by the Mach-Zehnder interferometer 900 is used, a high-speed characteristic of the quantum cryptographic communication can be realized by omitting the basic exchange unit and the basic exchange processing step existing in the conventional art and by effectively using all of the qubits.

embodiment Third

In the above embodiments, the qubit generation unit became the quantum-end device 100 made available. In this embodiment, the system can also be realized with a configuration in which the qubit generation unit in the quantum receiving device 200 Document 5: G. Ribordy, J.-D. Gautier, N. Gisin, O. Guinnard, H. Zbinden, "Automated" Plug & Play Quantum Key Distribution, Electronics Lett. 2116-2117, (1998).

4 shows an overall configuration diagram of the third embodiment. In this embodiment, as in FIG 4 1, a forward path and a return path between the quantum-end device and the quantum-receiving device are respectively provided as the quantum communication channels (a quantum communication channel in a forward path 105 and a quantum communication channel in a return path 106 ). However, it is also possible to realize a configuration in which an identical optical path is used as a forward path and a return path in which an optical path control unit such as a beam splitter, Faraday mirror, etc. is used.

In addition, in 4 the quantum demodulator 230 in the quantum communication channel in the return path 106 provided, the quantum demodulator 230 however, may also be provided in the quantum communication channel in the forward path.

In this embodiment the same effect as in the other embodiments can be realized.

Moreover, it is possible to have a processing load of the quantum sending device 100 to reduce by the qubit generation unit 40 in the quantum receiving device 200 is made available.

Industrial Applicability

According to this invention, it is possible to process the exchange of the bases between the Omit devices.

Furthermore the qubit can be used efficiently.

Furthermore Is it possible, a re-authentication communication in the classic Not need communication.

Furthermore Is it possible, to share the secrecy of the secure random information.

Claims (6)

Quantum-emitting device ( 100 ), comprising: a pseudorandom number generation unit ( 60 ) configured to generate a first pseudorandom number from secretly shared information previously secretly shared with a quantum receiving device ( 200 ) in synchronism with the generation of a second pseudorandom number by the quantum receiving device ( 200 ); a quantum coding unit ( 70 ) configured to perform quantum coding of a qubit selected as any two-level state of a photon or an electron; a quantum modulator ( 80 ) configured to perform quantum modulation of the qubit using the first pseudo-random number; a classic communication unit ( 130 ) intended for carrying out a classical communication with the quantum receiving device ( 200 ) via a classical communication network, and configured to receive one of a quantum measuring unit ( 240 ) of the quantum receiving device ( 200 ), which quantum measuring unit ( 240 ) is adapted to measure the qubit after performing a quantum demodulation by a quantum demodulator ( 230 ) of the quantum receiving device ( 200 ); and an error correcting unit ( 90 ) configured to perform error correction of the qubit using the first classical communication unit ( 130 ) received, the first classical communication unit ( 130 ) is adapted to communicate with the quantum receiving device ( 200 ), without the quantum receiving device ( 200 ) to authenticate. Quantum receiving device ( 200 ), comprising: a pseudorandom number generation unit ( 220 ) configured to generate a second pseudorandom number from secretly shared information previously secretly shared with a quantum sending device ( 100 ) in synchronism with the generation of a first pseudo-random number by the quantum-emitting device ( 100 ); a quantum demodulator ( 230 ) to which a qubit, which is selected as any two-level state of a photon or an electron, from the quantum-emitting device ( 100 ) adapted to perform quantum modulation of the qubit using the second pseudorandom number; a quantum measuring unit ( 240 ) configured to measure the qubit and output a measurement result; a classic communication unit ( 260 ) provided for performing a classical communication with the quantum-end device via a classical communication network and adapted to receive the qubit; and an error correcting unit ( 25 ) which is adapted to perform an error correction of the quantum measuring unit ( 240 ) using the classical communication unit ( 260 ) received qubits, the classical communication unit ( 260 ) is adapted to communicate with the quantum-emitting device ( 100 ), without the quantum-emitting device ( 100 ) to authenticate. A quantum cryptography communication system, comprising: a quantum-emitting device ( 100 ) configured to perform quantum coding, modulation and transmission of a qubit selected as any two-level state of a photon or an electron; and a quantum receiving device ( 200 ) configured to perform quantum modulation of the transmitted qubit, wherein the quantum-emitting device ( 100 ) a first pseudo-random number generation unit ( 60 ) configured to generate a first pseudorandom number from information previously secretly shared with the quantum receiving device (10). 200 ), a quantum coding unit ( 70 ) configured to perform quantum coding of the qubit, and a quantum modulator ( 80 ), which is designed for performing a quantum modulation of the qubit using the first pseudo-random number, and is adapted to transmit the modulated qubit to the quantum receiving device ( 200 ), wherein the quantum receiving device ( 200 ) a second pseudo-random number generation unit ( 220 ) configured to generate a second pseudorandom number from the secret information, in synchronism with the generation of the first pseudorandom number, and a quantum demodulator ( 230 ) configured to receive the signal from the quantum modulator ( 80 ) and for performing quantum modulation of the received qubit using the second pseudorandom number, the quantum receiving device further comprising a quantum measuring unit (12). 240 ), which is designed to measure the qubit and to output a measurement result, wherein the quantum-emitting device ( 100 ) further includes: a first classical communication unit ( 130 ) intended for carrying out a classical communication with the quantum receiving device ( 200 ) via a classical communication network ( 2 ) and configured to receive the signal from the quantum measuring unit ( 240 ) output measurement result; and a first error correcting unit ( 90 ) configured to perform error correction of the qubit using the first classical communication unit ( 130 ) received measurement result, wherein the quantum receiving device ( 200 ) further comprises: a second classical communication unit ( 260 ) provided for performing a classical communication with the quantum-end device ( 100 ) via the classical communication network ( 2 ) and configured to receive the qubit; and a second error correcting unit ( 250 ) which is adapted to perform an error correction of the quantum measuring unit ( 240 ) output using the second classical communication unit ( 260 ) received qubits; and wherein the first classical communication unit ( 130 ) is adapted to communicate with the quantum receiving device ( 200 ) without authentication of the quantum receiving device ( 200 ), and the second classical communication unit ( 260 ) is adapted to communicate with the quantum-emitting device ( 100 ) without authentication of the quantum sending device ( 100 ). A quantum cryptographic communication system according to claim 3, comprising a qubit generating unit ( 40 ) which is designed to periodically generate a qubit in either the quantum-emitting device ( 100 ) or the quantum receiving device ( 200 ), in the case where the qubit generating unit ( 40 ) in the quantum receiving device ( 200 ), the qubit generating unit ( 40 ) is configured to send the generated qubit to the quantum coding unit ( 70 ), and the quantum coding unit ( 70 ) is configured to perform quantum coding of the qubit generating unit ( 40 ) and in which case the qubit generating unit ( 40 ) in the quantum-emitting device ( 100 ), the quantum coding unit ( 70 ) is configured to perform quantum coding of the qubit generating unit ( 40 ) produced qubits. A quantum cryptographic communication system according to claim 4, wherein said qubit generating unit ( 40 ), the quantum modulator ( 80 ), the quantum demodulator ( 230 ) and the quantum measuring unit ( 240 ) are implemented with Mach-Zehnder interferometers. A quantum cryptography communication method comprising a quantum-end device ( 100 ) and a quantum receiving device ( 200 ) and comprises: performing ( 70 quantum coding of a qubit selected as any two-level state of a photon or an electron in the quantum-emitting device; Produce ( 60 ) a first pseudorandom number of information previously secretly shared by both devices in the quantum sending device; Carry out ( 80 ) quantum modulation of the qubit using the generated first pseudo-random number in the quantum-emitting device; Sending the qubit from the quantum sending device to the quantum receiving device; Produce ( 220 ) a second pseudo-random number from the secret shared information in the quantum receiving device, in synchronization with the generation of the first pseudo-random number; Carry out ( 230 ) quantum modulation of the qubit using the second pseudo-random number in the quantum receiving device; Establishing a classical connection over a network connecting the quantum sending device and the quantum receiving device between a first classical communication unit ( 130 ) in the quantum sending device and a second classical communication unit ( 260 ) in the quantum receiving device; Measure up ( 240 ) of the qubit in the quantum receiving device; Sending a measurement result from the quantum reception device to the first classical communication unit ( 130 ); Carry out ( 90 ) error correction of the qubit using the measurement result in the quantum well device; Sending the qubit to the second classical communication unit ( 260 ); and performing ( 250 ) an error correction of the measurement result in the quantum reception device; the first classical communication unit ( 130 ) with the quantum receiving device ( 200 ) without authentication of the quantum receiving device ( 200 ), and wherein the second classical communication unit ( 260 ) with the quantum-emitting device ( 100 ) without authentication of the quantum sending device ( 100 ) communicates.